A necessary component of the widely-used aluminum beverage can and similar cylindrical containers is the circular container end, sometimes called a "lid", which is seamed to the outermost edge of a cylindrical can body to form a fluid-tight container. Container ends are commonly formed from thin metal stock, for example aluminum or steel sheet, in a series of manufacturing operations. Typically, a circular blank is first cut from the metal stock. The blank is next formed into a shallow cup-shaped configuration having a generally flat center panel of circular shape, an annular countersink radius radially surrounding the center panel and extending axially (the axial direction being generally perpendicular to the center panel) below it, a seaming panel radially surrounding the countersink and extending axially above the center panel while also extending slightly radially outward, and a peripheral flange radially surrounding the seaming panel and extending radially outward. The peripheral flange is then curled downwardly at its peripheral edge to form a continuous lip suitable for later seaming to the container body.
In most production facilities, all of these initial operations are performed by an end-making machine, sometimes called a "shell press", having reciprocating die assemblies as is well known in the art. The resulting article, commonly called a "shell", can next be transferred to a liner machine (also well known in the art), which applies a sealing compound to the underside of the lip to improve sealing performance when the container end is seamed to the container body. At this point, the shell can be considered a finished container end for some applications, however, it is common for shells to be further processed to include an easy-opening feature such as a stay-on-tab opening or a ring-pull-tab opening. Shell-finishing machines, commonly called "conversion presses", are known in the art which utilize reciprocating die assemblies and other mechanisms to successively form contoured panels, score lines, rivets, and other features on the flat center panel of the shell and to form and attach accessories such as tabs or rings as necessary to produce the desired container end configuration. For purposes of this application, the term "end" will be used herein to refer to a shell, a finished container end with an easy-opening device, and all intermediate products in different stages of manufacture therebetween. In addition, when referring to the orientation of a container end, the terms "front" and "top" will be used interchangeably to denote the surface of the container end intended to face outwardly on an assembled container, while the terms "back" and "bottom" will be used to denote the surface of the container end intended to face inwardly on an assembled container.
Because of the slight outward inclination of the seaming panel and the axial offset between the center panel and the peripheral flange on each container end, a pair of such container ends which are oriented in the same axial direction can be "nested" one behind the other with the generally convex back portion of one container end projecting into the generally concave front portion of the other container end. Any number of like-oriented container ends can be nested together in this fashion. When nested, a container end is slidably engaged in the axial direction with respect to its immediate neighbors; however, it is mechanically interlocked in the lateral direction (the lateral direction being perpendicular to the axial direction) such that it is prevented from moving laterally independent of its neighbors. Nesting provides some significant advantages in the handling of container ends. In addition, nesting greatly decreases the volume occupied by a group of container ends. In some cases, nested container ends occupy less than about one-third of the volume occupied by a like amount of container ends which are not nested.
Bulk quantities of nestable container ends can be placed in an axially aligned group, sometimes called a "stick", which facilitates handling of the bulk container ends, both by manual means and by automated handling equipment. Sticks can be of any size, with some incorporating up to 660 lids each. Sticks of finished or semi-finished container ends can be taken from the production process at various points and placed in trays for short term storage or local transfer to other equipment. Alternatively, sticks of container ends can be packaged, typically in tubular paper bags, for long term storage or for shipment to A other facilities. These stored container ends can subsequently be used as infeed for further production operations by removing them from the packaging and introducing them into automated equipment such as conversion presses and canning equipment.
As axially aligned groups of container ends are subjected to handling, packaging and unpackaging, it is not uncommon for one or more of the container ends in such a group to be "flipped over" or reversed such that it has an orientation which is the opposite of that held by its neighbors. The axial surfaces of a reversed container end will match exactly with the axial surfaces of adjacent non-reversed container ends. As a consequence, the reversed container end or ends will no longer nest with the neighboring container ends. Since a reversed container end is not laterally interlocked with the adjacent container ends, then a axially aligned group of container ends incorporating one or more reversed container ends cannot withstand any significant shear forces and is much more likely to burst or fall apart during handling, causing the container ends to be scattered and disrupting production. Further, a reversed container end in an axially aligned group may eventually be fed into a piece of automated equipment, which can cause significant production losses as described below.
Container ends being fed into high-speed automated equipment (e.g., conversion presses) are often moved in continuous axial lines (i.e., an axial arrangement that is being constantly replenished at one point such that it can provide a continuous supply at another point) through tubular supply trackwork or conduits up to the point of introduction into the actual equipment. In some systems, the container ends being conveyed are urged through the trackwork by the force of gravity alone. In other systems, mechanical or pneumatic devices, sometimes called "pushers", are employed to maintain an axial force on the container ends to push them through the trackwork. This axial force exceeds 40 pounds in some systems. Even when pusher devices are employed, however, the lids in the conveyed line may not move smoothly or continuously through the trackwork. Instead, the lids are subject to intermittent surging caused by the operation of upstream and downstream equipment. During surges, the lids in the trackwork may temporarily stop, move forward suddenly, or even move backward a short distance. The container ends in this supply line are intended to be maintained in a common orientation (i.e., either the front side of all lids or the back side of all lids facing in the direction of conveyance) such that the container ends will feed into the subject equipment with a known orientation. However, a reversed container end which enters the supply conduit can be carried along by the remaining container ends even though it has the wrong orientation and is not nested.
The consequences of feeding an improperly oriented container end into automated equipment can range from simply spoiling the end in question to jamming or even damaging the equipment and/or its tooling. As a result, most container end supply lines include sensors and control systems which automatically shut down the supply line and associated equipment when a reversed end is detected. Plant personnel, alerted each time the equipment shuts down, then remove the reversed end from the supply line and restart the equipment.
Regardless of whether container end manufacturing equipment is shut down due to a reversed end which has jammed inside the mechanism, or merely due to the detection of a reversed end in the supply line, the down-time and product spoilage associated with clearing a reversed end and restarting the equipment can represent a significant loss of productivity. For example, a typical conversion press can produce 615 container ends per minute in each lane and can have up to three lanes. Each time a reverse-oriented container end caused the equipment to stop, then all three lanes will be shut down, sometimes for as much as 15 minutes, while the jam or reversed end is cleared and the machine is prepared for restarting. The 15 minutes of down time on a three-lane press operating at 615 ends per minute represents a loss of over 27,000 unproduced container ends. In addition, several dozen container ends will be spoiled as the conversion press comes up to its nominal speed. Further, operations of equipment upstream and downstream of the machine in question may also be disrupted. Accordingly, it is very desirable to remove reversed container ends from the conveyed line of ends in the supply conduit prior to the point of introduction into the actual processing equipment and without shutting down the associated equipment.
Systems for detecting and removing reversed container ends from a continuous flow of otherwise similarly aligned and nested container ends are known. For example, U.S. Pat. No. 4,977,998 discloses a system incorporating a coaxially mounted detector and ejector having a striker member which rapidly contacts a reversed end to cause its ejection from the flow of ends. U.S. Pat. No. 4,655,350 discloses a system incorporating an optical detector and an ejector having a striker member for contacting and ejecting a reversed container end from a moving line of ends. In such systems, however, the impact of the striker member, especially if it hits the peripheral flange of the end, can dent or otherwise deform the end, its flange and/or lip, thus making the end unsuitable for further use. This is especially true if the container ends are being held together with significant axial force such as is supplied by a pusher device. In such cases, the impact force of the striker member must be increased accordingly to overcome the friction between the container ends and achieve ejection. This increased striking force greatly increases the likelihood that the reversed container ends will be damaged by the striker during ejection. In addition, the striker must be precisely aligned with the reversed container end at the time of ejection to hit the right portion and to avoid striking and damaging a non-reversed end adjacent to the reversed end. Damaged non-reversed ends will not be ejected from the supply line and can cause production problems in a later operation, for example when the container end is seamed to a container body. A need therefore exists, for a reversed container end ejection system which does not rely on physical impact to eject the reversed ends. Further, a need exists for an ejection system which allows for some misalignment between the reversed container end and the ejector.
U.S. Pat. No. 5,145,050 discloses a system incorporating a hook member which engages the curled lip of a reversed container end and pulls it from the moving line or raises the reversed end in the line for removal by a secondary hook. While the disclosed system does not rely on direct impact to eject the reversed end, the extraction force exerted by the hook on the lip of the end may also damage or deform the container end so that it is no longer useable. This is especially true if the container ends are being held together with significant axial force by a pusher device as previously discussed. In such cases the hook will have to pull with a much greater force to remove or lift the reversed end. Further, if the force of the pusher is high enough, then the hook will merely pull through the curled edge of the lid without lifting or removing it. This will allow a damaged reversed container end to remain in the supply line. A need therefore exists for a reversed container end ejection system which does not directly contact any portion of the ends to be ejected. A need further exists for an ejection system which functions in the presence of significant axial forces on the line of ends.
As previously described, an axially aligned group of container ends being conveyed is subject to surges which can cause sudden stops, sudden forward movement or backward movement of the ends. In prior art reversed-end ejection systems, the sudden stop or reversal of the container ends can cause a striker member to miss its intended target, or can cause a hook member to become disengaged from the lip of a reversed end. In either case, the reversed container end may not be ejected, and either or both of the reversed container end and adjacent non-reversed container ends can be damaged. In addition, if the system uses a sensor to detect when the reversed container end is in position for ejection, then the sensor must recognize and account for backward motion of the container ends caused by surging. A need therefore exists, for a reversed container end ejector system which functions even in the presence of surges in the axially aligned group of container ends.
Further, several reversed container ends will occasionally be nested together within an axially aligned group forming a reversed sub-group. Prior reversed container end ejection systems involved the striking or hooking of the specific container ends to be ejected and do not provide for the ejection of a reversed sub-group comprising several reversed container ends nested together. A need therefore exists for a reversed container end ejection system which can eject a reversed sub-group comprising several reversed container ends.